1. Field of the Invention
The present invention relates to an environment recognition device and an environment recognition method for recognizing a target object based on luminances of the target object in a detection area.
2. Description of Related Art
Conventionally, a technique has been known that detects a target object such as an obstacle including a vehicle and a traffic light located in front of a subject vehicle for performing control to avoid collision with the detected target object and to maintain a safe distance between the subject vehicle and the preceding vehicle (for example, Japanese Patent No. 3349060 (Japanese Patent Application Laid-Open (JP-A) No. 10-283461).
Further, in such techniques, there is a technique that performs more advanced control. Specifically, it not only specifies a target object uniformly as a solid object, but further determines whether the detected target object is a preceding vehicle that is running at the same speed as the subject vehicle or a fixed object that does not move. In this case, when the target object is detected by capturing an image of a detection area, it is necessary to extract (cut out) the target object from the captured image before specifying what the target object is.
For example, there is known a technique that recognizes, when the captured image is a color image, a light source such as a traffic light as a target object by grouping a set of pixels with a same luminance (color) (for example, JP-A No. 2010-224925). However, when a resolution of the image capturing device that captures the detection area is low, or when the captured light source is located at distance, a luminance (color) and size of a light source which is different from a traffic light are unlikely to correctly be recognized and may be similar to the luminance and size of a lighting portion of the traffic light. In this case, simply grouping plural pixels having similar color characteristics may cause the light source, which should be recognized a light source different from a traffic light, to be falsely recognized as the traffic light.